1. Field of the Invention
This invention relates to improvements in a filter arrangement disposed in a fuel tank and connected to a fuel pump in a fuel supply system, for example, of an automotive vehicle, and more particularly to such a filter arrangement which is prevented from collapsing even under vacuum due to sucking action of a fuel pump.
2. Description of the Prior Art
As a filter arrangement disposed inside a fuel tank and connected to a fuel pump, a variety of ones have been proposed and put into practical use. One of them is disclosed in Japanese Utility Model Provisional Publication No. 61-26617. In this publication, the filter arrangement includes a cap-shaped upper section located facing the upper side of a fuel tank. A lower section made of a mesh is connected to the open periphery of the cap-shaped upper section so that a hollow chamber is defined between the upper and lower sections. This filter arrangement is installed on a fuel pump at the suction port in such a manner that the lower section is spaced from the bottom inner surface of the fuel tank.
In this case, fuel between the lower section and the tank bottom inner surface cannot be effectively sucked into the fuel pump. In order to effectively suck the fuel in this region, the filter arrangement shown in FIG. 7 was conceived. In this filter arrangement, an upper section 2' and a lower section 3' both made of mesh are symmetrically formed, and secured to each other to form a bag-shaped filter 1'. The filter 1' is connected to a suction pipe 8' of a fuel pump 7' in such a manner as to be brought into elastic contact with the bottom inner surface of the fuel tank 4' so as to achieve vibration damping in addition to effective sucking of fuel.
Difficulties have been encountered even in such a filter 1', since the upper and lower sections 2', 3' unavoidably collapse inwards to come into contact with each other under a vacuum generated by the fuel pump 7'. As a result, the flow passage for fuel is blocked and the supply of fuel to the vehicle is cut off. In order to prevent such difficulties, the suction pipe 8' may be extended inside the filter 1' to suppress the collapse of the netting upper and lower section 2', 3' as indicated by phantom lines in FIG. 7. However, the extended suction pipe 8' tends to cause cavitation and vapor lock.